With the ever increasing interest in both pollution control and fuel savings, a great deal of attention has been focussed on every aspect of the fuel combustion process. Fuel injection is one area of major interest and a number of different approaches have been taken. One problem of particular concern is the provision of rapid mixing of the fuel and air in the combustion chamber so as to promote cleaner burning and to prevent the formation of fuel rich pockets of the fuel/air mixture within the chamber. Two fuel injection techniques of particular interest here are the use of fuel injectors providing high pressure drops and/or the use of high air velocities (so-called "air blast" injectors) to create small droplets of fuel that will mix and evaporate rapidly.
A serious disadvantage associated with the use of high pressure drops is that the small orifice sizes which are required to produce such drops tend to clog. Further, with such high chamber pressures, mixing and penetration of the fuel is generally poor, resulting in smoke and the fuel rich pockets referred to above, and thus producing greater amounts of pollutants. In air blast injectors, the fuel must be distributed on a surface edge and this, again, requires small clearances to provide distribution of fuel and hence the same problems with regard to clogging and blockage are encountered.
A further discussion of the prior art and the problems associated with fuel injection in high performance gas turbines is contained in U.S. Pat. No. 3,283,502 (Lefebvre). Other patents of possible interest include U.S. Pat. Nos. 2,771,741 (Barnard 4th), 3,469,394 (Beheim), 3,961,475 (Wood) and 3,937,007 (Kappler), although this listing is not, and is not represented to be, exhaustive.